In recent years, there have been various endeavors to use nonaqueous electrolyte secondary batteries in, for example, electric vehicles, hybrid cars, and the like. In such applications, the batteries are required to have superior storage stability in addition to high output.
For example, JP-A-11-67270 discloses that the storage characteristics of a nonaqueous electrolyte secondary battery are improved by adding lithium difluorophosphate to its nonaqueous electrolyte.